Figure 1.
Dakosaurus andiniensis, referred specimen MOZ 6146P.
Skull and mandible in, (A) lateral (right) view of the snout and (B) close-up on the posterior teeth, showing the interlocking dentition. Note the robust teeth and snout. Abbreviations: max, maxilla; mnf, maxillary neurovascular foramen; na, nasal; orb, orbit; pof, preorbital fenestra; prf, prefrontal.
Figure 2.
Dakosaurus maximus, neotype SMNS 8203.
(A) General view of the skull and mandible, (B) close-up on the dentary alveoli and raised lateral and medial margins, and (C) oblique forward view of the dentary tooth row. Abbreviations: den, dentary; dlp, dentary lateral plate; dmp, dentary medial plate; max, maxilla; na, nasal; pre, premaxilla; prf, prefrontal; tc, tooth crowns.
Figure 3.
Dakosaurus maximus, neotype SMNS 8203.
(A) Anterior view of the skull and mandible, note that level to the fourth dentary tooth the mandibular ramus deflects laterally (i.e. short symphysis), and (B) oblique dorsal view of the skull, emphasising the blunt “bullet-shaped” snout (i.e. amblygnathy). Abbreviations: den, dentary; max, maxilla; na, nasal; pre, premaxilla; prf, prefrontal.
Figure 4.
Dakosaurus maximus, neotype SMNS 8203.
(A) Close-up on the premaxillary ‘lateral plates’, (B) close-up on the maxillary alveoli in oblique ventral view and (C) close-up on the maxillary teeth showing tooth crown wear. Abbreviations: plp, premaxillary lateral plate; rp, reception pit.
Figure 5.
Dakosaurus maximus, referred specimens SMNS 10819a and SMNS 10819b.
Snout (SMNS 10819a) in: (A) dorsal view, (B) ventral (palatal) view, and (C) close-up on the maxillary tooth-row in ventral view. Note that several teeth exhibit carinal wear, broken apices and spalling of the enamel at the apex. (D) Left-half of the posterior region of the skull (SMNS 10819b) in dorsal view. Abbreviations: en, external nares; fr, frontal; max, maxilla; pa, parietal; po, postorbital; pre, premaxilla; prf, prefrontal; rp, reception pit; sq, squamosal; stf, supratemporal fenetra.
Figure 6.
Dakosaurus maximus, referred specimen SMNS 82043.
Left mandibular ramus in lithographic limestone in: (A) general view, (B) close-up on the anterior teeth, and (C) close-up on the dentary dorsal margin at the first preserved tooth crown, showing the various foramina and a reception pit and (D) close-up on the dentary dorsal margin, slightly further back along the tooth row. Abbreviations: an, angular; art, articular; cp, coronoid process on the surangular; den, dentary; rp, reception pit; sdg, surangulodentary groove; sur, surangular.
Figure 7.
Dakosaurus maximus, referred specimen SMNS 56999.
Left isolated maxilla in: (A) lateral view, (B) dorsal view and (C) ventral view (showing the tooth row). Abbreviations: al, alveolus; mnf, maxillary neurovascular foramen; pof, preorbital fenestra; tc, tooth crown.
Figure 8.
Dakosaurus maximus, referred specimens SMNS 91425.
Numerous isolated teeth of D. maximus showing the occlusion wear patterns and apical breakage. Top left scale bar for (A), top right scale bar for (B), and bottom scale bar for images (C)–(D). Abbreviations: bf, basal facet; btc, broken tip; cw, carinal wear.
Figure 9.
Plesiosuchus manselii, holotype NHMUK PV OR40103.
Dorsal view of the skull, (A) hypothetical skull reconstruction (grey lines represent elements that are missing) and (B) photograph of what is preserved. Abbreviations: en, external nares; max, maxilla; na, nasal; orb, orbit; pa, parietal; pre, premaxilla; prf, prefrontal; sq, squamosal; stf, supratemporal fenestra.
Figure 10.
Plesiosuchus manselii, holotype NHMUK PV OR40103.
Snout in dorsal view, (A) line drawing (grey squares represent the premaxilla-maxilla suture, the exact nature of which we are unsure) and (B) photograph. Abbreviations: en, external nares; fr, frontal; max, maxilla; na, nasal; pre, premaxilla; prf, prefrontal.
Figure 11.
Plesiosuchus manselii, holotype NHMUK PV OR40103.
Snout in lateral (right) view, (A) photograph and (B) line drawing (grey shaded area represents the orbital cavity, grey lines represents sutures we are unsure of). Abbreviations: al, alveolus; max, maxilla; na, nasal; orb, orbit; pal, palatine; pre, premaxilla; prf, prefrontal; sut?, suture?; tc, tooth crown.
Figure 12.
Plesiosuchus manselii, holotype NHMUK PV OR40103.
Snout in ventral (palatal) view, (A) line drawing (grey lines represent the sutures we are unsure of) and (B) photograph. Abbreviations: al, alveolus; max, maxilla; pal, palatine; pre, premaxilla; sof, suborbital fenestra; sut?, suture?; tc, tooth crown.
Figure 13.
Plesiosuchus manselii, holotype NHMUK PV OR40103.
Braincase: in (A) dorsal view, (B) ventral view and (C) occipital view. Abbreviations: bt, basal tubera; eo, exocciptial; fm, foramen magnum; pa, parietal; qu, quadrate; soc, supraoccipital; sq, squamosal; stf, supratemporal fenestra.
Figure 14.
Plesiosuchus manselii, referred specimen NHMUK PV R1089.
Braincase and intertemporal bar in: (A) dorsal view and (B) ventral view. Abbreviations: bt, basal tubera; crB, crest B; fr, frontal; ic, foramen for the internal carotid artery; oc, occipital condyle; pa, parietal; pop, paroccipital process; qu, quadrate; quas, quadrate articular surface; sq, squamosal.
Figure 15.
Plesiosuchus manselii, referred specimen NHMUK PV R1089.
Close-up on the articular surface of the right quadrate. Abbreviations: bt, basal tubera; crB, crest B; oc, occipital condyle; qu, quadrate; quas, quadrate articular surface; sq, squamosal.
Figure 16.
Plesiosuchus manselii, referred specimen NHMUK PV R1089.
Braincase in occipital view, (A) photograph and (B) line drawing (filled grey areas represent foramina). Abbreviations: XI?, foramen for cranial nerve XI?; art, articular; bo, basioccipital; bt, basal tubera; dso, depression for the supraoccipital; eo, exoccipital; fm, foramen magnum; ic, foramen for the internal carotid artery; oc, occipital condyle; pa, parietal; pop, paroccipital process; qu, quadrate; quas, quadrate articular surface; sq, squamosal; sut?, suture?.
Figure 17.
Plesiosuchus manselii, holotype NHMUK PV OR40103a.
Mandible, with the left ramus is lateral view and the right ramus in medial view.
Figure 18.
Plesiosuchus manselii, holotype NHMUK PV OR40103a.
Mandible, right ramus in lateral view.
Figure 19.
Plesiosuchus manselii, referred specimen NHMUK PV R1089.
Posterior half of the left mandibular ramus in: (A) lateral view, (B) medial view, (C) dorsal view and (D) ventral view.
Figure 20.
Plesiosuchus manselii, referred specimen NHMUK PV R1089.
Posterior half of the right mandibular ramus in: (A) lateral view, (B) medial view, (C) dorsal view and (D) ventral view.
Figure 21.
Plesiosuchus manselii, referred specimen NHMUK PV R1089.
Mandibular symphysis in dorsal view, (A) line drawing and (B) photograph. Abbreviations: al, alveolus; co, coronoid, den, dentary; sp, splenial.
Figure 22.
Plesiosuchus manselii, holotype NHMUK PV OR40103a.
Isolated tooth crown in: (A) right lateral view, (B) left lateral view and (C) dorsal (apical) view.
Figure 23.
Plesiosuchus manselii, holotype NHMUK PV OR40103a.
Close-up on the carinae of an isolated tooth crown, (A) anterior carina and (B) posterior carina.
Table 1.
List of characters to differentiate between the various Geosaurini genera present in the Late Jurassic of Europe.
Table 2.
Table of diagnostic characters for Metriorhynchidae, and various subclades, for the three Kimmeridge Bay NHMUK PV specimens.
Figure 24.
Gracilineustes leedsi, holotype NHMUK PV R3540.
Snout in ventral (palatal) view, (A) photograph and (B) line drawing (thin grey lines represent breaks). Abbreviations: al, alveolus; max, maxilla; pal, palatine; ptg, pterygoid.
Figure 25.
cf. Plesiosuchus manselii, MUJA-1004.
Isolated tooth in: (A) lingual view, (B) labial view, (C) distal view, and (D) basal view. Close-up on the denticulated carinae, showing: (E) middle of the distal carina, (F) base of the distal carina, and (G) middle of the mesial carina. Scale bar: 5 mm (A–D) and 0.5 mm (E–G). Figure modified from Figure 1 in Ruiz-Omeñaca et al. [28].
Figure 26.
Strict consensus of 22 most parsimonious cladograms, showing the phylogenetic relationships of Plesiosuchus manselii and Dakosaurus maximus within Metriorhynchidae when all characters are unordered.
Note that while both are members of the subclade Geosaurini, P. manselii is in an unresolved position with Torvoneustes, Geosaurus and Dakosaurus (D. andiniensis + D. maximus). Length = 627; ensemble consistency index, CI = 0. 506; ensemble retention index, RI = 0. 860; rescaled consistency index, RC = 0. 435. The black arrow points to the only consistent difference in the 50% majority rule consensus topology: the slightly greater resolution in Rhacheosaurini. Bootstrap-values are given above or below the relevant node.
Figure 27.
Strict consensus of 195 most parsimonious cladograms, showing the phylogenetic relationships of Plesiosuchus manselii and Dakosaurus maximus within Metriorhynchidae when 40 characters are ordered.
Length = 667; ensemble consistency index, CI = 0. 481; ensemble retention index, RI = 0. 863; rescaled consistency index, RC = 0. 415. Bootstrap-values are given above or below the relevant node.
Figure 28.
50% majority rule consensus topology of 195 most parsimonious cladograms, showing the phylogenetic relationships of Plesiosuchus manselii and Dakosaurus maximus within Metriorhynchidae when 40 characters are ordered.
Length = 667; ensemble consistency index, CI = 0. 481; ensemble retention index, RI = 0. 863; rescaled consistency index, RC = 0. 415. The black circles at certain nodes denote clades that break in the strict consensus topology. Bootstrap-values are given above or below the relevant node.
Figure 29.
Genus-level evolutionary relationships of Metriorhynchidae, based on the phylogenetic analysis presented herein.
The time-span of genera with question marks is uncertain, and the grey bars are range extensions.
Figure 30.
Life reconstructions showing the maximum body lengths for the four Geosaurini genera present in the late Kimmeridgian-early Tithonian of Western Europe.
The species from top to bottom are: Geosaurus giganteus, Dakosaurus maximus, Torvoneustes carpenteri and Plesiosuchus manselii. The maximum known body lengths of Torvoneustes and Geosaurus are from Young et al. [14], while those of Dakosaurus and Plesiosuchus are from this paper. The human diver is 1.8 m in height. All metriorhynchid life reconstructions are by Dmitry Bogdanov.
Table 3.
Table of data derived from the optimum gape calculations.
Figure 31.
Lateral reconstructions of the skull of Plesiosuchus manselii, Dakosaurus maximus and D. andiniensis.
Line drawings: (A) Plesiosuchus manselii is an original skull reconstruction based on the mandible of NHMUK PV OR40103a, while the skull is a composite of NHMUK PV OR40103 and D. andiniensis (due to the holotype lacking part of the orbital and infratemporal regions of the skull, these regions are shown by broken lines); (B) Dakosaurus maximus is an original skull reconstruction based on the mandible of SMNS 8203 and SMNS 82043, while the skull is a composite of SMNS 8203, SMNS 10819b and D. andiniensis (due to the neotype and referred specimen lacking the lower orbital and infratemporal regions, these regions are shown by broken lines); (C) Dakosaurus andiniensis, redrawn from Pol & Gasparini [20].